PROJECT SUMMARY The research program to be continued through this competitive renewal focuses on abnormalities in nociceptin/orphanin FQ (N/OFQ) function as a factor in ethanol (EtOH) addiction, and the treatment target potential of this system for EtOH abuse. Studies during the previous funding period investigated the functional status of the N/OFQ system in Marchigian Sardinian Alcohol Preferring (msP) and stock Wistar rats, as well as N/OFQ system activation as a means to reduce EtOH-related addictive behavior. Nociceptin opioid receptor (NOP) agonists reliably reduced voluntary EtOH drinking. However, in msP rats that carry an innate upregulation of the N/OFQ system, these effects required chronic administration. At the same time, rats with NOP receptor deletion (NOP-KO rats) consumed significantly less EtOH than wild-type controls. Thus, the ?therapeutic? actions of NOP agonists seem to depend on their eventual downregulation of the N/OFQ system. Consequently, acute suppression of N/OFQ transmission by NOP antagonists would be expected to produce the same inhibitory effects on EtOH-motivated behavior as chronic agonist-induced downregulation of this system. Preliminary data that acute NOP receptor blockade reduces EtOH intake in msP rats tentatively confirmed this hypothesis. Capitalizing on these findings, this project is designed to investigate the ?therapeutic? potential of NOP antagonists and the association between N/OFQ function and EtOH-motivated addictive behavior. SPECIFIC AIM 1 will establish the effects of acute NOP receptor blockade on EtOH consumption, motivation to obtain EtOH under increasing workloads, and EtOH craving measured by contextual reinstatement of EtOH seeking. This Aim will also establish whether rats with innate (msP rats) or EtOH-induced (postdependent Wistar rats) N/OFQ system upregulation, are more sensitive to the effects of NOP blockade than rats with normal N/OFQ function (nondependent Wistar rats). SPECIFIC AIM 2 will establish the effects of chronic NOP antagonist treatment -- likely to be employed in treatment settings -- on EtOH- motivated behaviors to generate translationally relevant information. In parallel, this Aim will establish whether chronic NOP antagonist exposure produces adaptive changes in the N/OFQ system that may have implictions for the therapeutic potential of NOP receptor blockade. SPECIFIC AIM 3 will investigate how N/OFQ system upregulation enhances vulnerability to EtOH drinking and seeking. This Aim will also to identify the brain areas in which dysregulation of the N/OFQ system is responsible for enhanced vulnerability to these behaviors, and thereby shed light on critical sites for the inhibitory actions of NOP blockade on EtOH-motivated behavior. Overall, the research plan is designed to advance current understanding of the treatment target potential of the N/OFQ system for alcohol use disorder and the role of this system in predisposition vulnerability to develop EtOH dependence. NOP antagonists are in Phase 2 clinical trials such that the proposed work may have significant relevance for future development of these compounds towards treatments for alcohol use disorder.